Hybrid energy off highway vehicle electric power storage system and method

ABSTRACT

An electrical energy capture system for use in connection with a hybrid energy off highway vehicle system of a off highway vehicle. The hybrid energy off highway vehicle system includes an off highway vehicle, a primary power source, and an off highway vehicle traction motor propelling the off highway vehicle in response to the primary electric power. The off highway vehicle traction motor has a dynamic braking mode of operation generating electrical energy. The electrical energy capture system includes an energy management processor carried on the off highway vehicle. The capture system also includes an off highway vehicle electric generator connected to and driven by the primary power source for selectively supplying primary electric power, wherein the generator is responsive to said processor. An electrical energy storage device is carried on a off highway vehicle and is in electrical communication with the off highway vehicle traction motor. The storage device is responsive to the processor, selectively stores electrical energy generated in the dynamic braking mode, and selectively provides secondary electric power from said stored electricity electrical energy to the off highway vehicle traction motor. The off highway vehicle traction motor is responsive to the secondary electric power. The processor provides a first control signal to the electrical energy storage device to control the selective storing of the electrical energy generated in the dynamic braking mode, and to control the selective providing of secondary electric power to the off highway vehicle traction motor. The processor also provides a second control signal to the generator for controlling the selective supplying of primary electric power to the off highway vehicle traction motor.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The invention of the present application is aContinuation-in-Part that claims of U.S. patent application Ser. No.10/033,347, filed on Dec. 26, 2001, and entitled “HYBRID ENERGYLOCOMOTIVE POWER STORAGE SYSTEM”, which claims priority from U.S.Provisional Application Serial No. 60/278,975, filed on Mar. 27, 2001,the entire disclosure of which is incorporated herein by reference.

[0002] The following commonly owned, co-pending applications are relatedto the present application and are incorporated herein by reference:

[0003] Attorney docket 4066CIP/GETS 5290.2, filed on Mar. 3, 2003, andentitled “HYBRID ENERGY OFF HIGHWAY VEHICLE POWER MANAGEMENT SYSTEM ANDMETHOD”;

[0004] U.S. patent application Ser. No. 10/033,172, filed on Dec. 26,2001, and entitled “HYBRID ENERGY POWER MANAGEMENT SYSTEM AND METHOD”,allowed Dec. 23, 2002;

[0005] U.S. patent application Ser. No. 10/033,347, filed on Dec. 26,2001, and entitled “HYBRID ENERGY LOCOMOTIVE POWER STORAGE SYSTEM”;

[0006] U.S. patent application Ser. No. 10/033,191, filed on Dec. 26,2001, and entitled “HYBRID ENERGY LOCOMOTIVE SYSTEM AND METHOD”; and

[0007] U.S. patent application Ser. No. 10/032,714, filed on Dec. 26,2001, and entitled “LOCOMOTIVE ENERGY TENDER”.

FIELD OF THE INVENTION

[0008] The invention relates generally to energy management systems andmethods for use in connection with a large, Off-Highway Vehicle such asa railway locomotive, mining truck or excavator. In particular, theinvention relates to a system and method for managing the storage andtransfer of electrical energy, such as dynamic braking energy or excessprime mover power, produced by Off-Highway Vehicles driven by electrictraction motors.

BACKGROUND OF THE INVENTION

[0009]FIG. 1A is a block diagram of an exemplary prior art Off HighwayVehicle. In particular, FIG. 1A generally reflects a typical prior artdiesel-electric Off Highway Vehicle. Off Highway Vehicles includelocomotives and mining trucks and excavators, where mining trucks andexcavators range from 100-ton capacity to 400-ton capacity, but may besmaller or larger. Off Highway Vehicles typically have a power weightratio of less than 10 h.p. per ton with a ratio of 5 h.p. per ton beingcommon. Off Highway Vehicles typically also utilize dynamic or electricbraking. This is in contrast to a vehicle such as a passenger bus thathas a ratio of 15 h.p. per ton or more and utilizes mechanical orresistive braking.

[0010] As illustrated in FIG. 1A, the Off Highway Vehicle 100 includes adiesel primary power source 102 driving an alternator/rectifier 104. Asis generally understood in the art, the alternator/rectifier 104provides DC electric power to an inverter 106 that converts the ACelectric power to a form suitable for use by a traction motor 108. Onecommon Off Highway Vehicle configuration includes one inverter/tractionmotor per wheel 109, with two wheels 109 comprising the equivalent of anaxle (not shown). Such a configuration results in one or two invertersper Off Highway Vehicle. FIG. 1A illustrates a single inverter 106 and asingle traction motor 108 for convenience. By way of example, largeexcavation dump trucks may employ motorized wheels such as the GEB23™ ACmotorized wheel employing the GE150AC™ drive system (both of which areavailable from the assignee of the present system).

[0011] Strictly speaking, an inverter converts DC power to AC power. Arectifier converts AC power to DC power. The term “converter” is alsosometimes used to refer to inverters and rectifiers. The electricalpower supplied in this manner may be referred to as prime mover power(or primary electric power) and the alternator/rectifier 104 may bereferred to as a source of prime mover power. In a typical ACdiesel-electric Off Highway Vehicle application, the AC electric powerfrom the alternator is first rectified (converted to DC). The rectifiedAC is thereafter inverted (e.g., using power electronics such asInsulated Gate Bipolar Transistors (IGBTs) or thyristors operating aspulse width modulators) to provide a suitable form of AC power for therespective traction motor 108.

[0012] As is understood in the art, traction motors 108 provide thetractive power to move Off Highway Vehicle 100 and any other vehicles,such as load vehicles, attached to Off Highway Vehicle 100. Suchtraction motors 108 may be an AC or DC electric motors. When using DCtraction motors, the output of the alternator is typically rectified toprovide appropriate DC power. When using AC traction motors, thealternator output is typically rectified to DC and thereafter invertedto three-phase AC before being supplied to traction motors 108.

[0013] The traction motors 108 also provide a braking force forcontrolling speed or for slowing Off Highway Vehicle 100. This iscommonly referred to as dynamic braking, and is generally understood inthe art. Simply stated, when a traction motor 108 is not needed toprovide motivating force, it can be reconfigured (via power switchingdevices) so that the motor operates as an electric power generator. Soconfigured, the traction motor 108 generates electric energy which hasthe effect of slowing the Off Highway Vehicle. In prior art Off HighwayVehicles, such as illustrated in FIG. 1A, the energy generated in thedynamic braking mode is typically transferred to resistance grids 110mounted on the vehicle housing. Thus, the dynamic braking energy isconverted to heat and dissipated from the system. Such electric energygenerated in the dynamic braking mode is typically wasted.

[0014] It should be noted that, in a typical prior art DC hybridvehicle, the dynamic braking grids 110 are connected to the tractionmotors 108. In a typical prior art AC hybrid vehicle, however, thedynamic braking grids are connected to the DC traction bus 122 becauseeach traction motor 108 is normally connected to the bus by way of anassociated inverter 106 (see FIG. 1B). FIG. 1A generally illustrates anAC hybrid vehicle with a plurality of traction motors; a single inverteris depicted for convenience.

[0015]FIG. 1B is an electrical schematic of a typical prior art OffHighway Vehicle 100. It is generally known in the art to employ a singleelectrical energy source 102, however, two or more electrical energysources may be employed. In the case of a single electrical energysource, a diesel engine 102 coupled to an alternator 104 provides theprimary source power 104. In the case where two or more electricalenergy sources 102 are provided, a first system comprises the primemover power system that provides power to the traction motors 108. Asecond system (not shown) provides power for so-called auxiliaryelectrical systems (or simply auxiliaries). Such an auxiliary system maybe derived as an output of the alternator, from the DC output, or from aseparate alternator driven by-the primary power source. For example, inFIG. 1B, a diesel engine 102 drives the prime mover power source 104(e.g., an alternator and rectifier), as well as any auxiliaryalternators (not illustrated) used to power various auxiliary electricalsubsystems such as, for example, lighting, air conditioning/heating,blower drives, radiator fan drives, control battery chargers, fieldexciters, power steering, pumps, and the like. The auxiliary powersystem may also receive power from a separate axle driven generator.Auxiliary power may also be derived from the traction alternator ofprime mover power source 104.

[0016] The output of prime mover power source 104 is connected to a DCbus 122 that supplies DC power to the traction motor subsystems124A-124B. The DC bus 122 may also be referred to as a traction bus 122because it carries the power used by the traction motor subsystems. Asexplained above, a typical prior art diesel-electric Off Highway Vehicleincludes two traction motors 108, one per each wheel 109, wherein thetwo wheels 109 operate as an axle assembly, or axle-equivalent. However,a system may be also be configured to include a single traction motorper axle or configured to include four traction motors, one per eachwheel 109 of a two axle-equivalent four-wheel vehicle. In FIG. 1B, eachtraction motor subsystem 124A and 124B comprises an inverter (e.g.,inverter 106A and 106B) and a corresponding traction motor (e.g.,traction motor 108A and 108B, respectively).

[0017] During braking, the power generated by the traction motors 108 isdissipated through a dynamic braking grid subsystem 110. As illustratedin FIG. 1B, a typical prior art dynamic braking grid subsystem 110includes a plurality of contactors (e.g., DB1-DB5) for switching aplurality of power resistive elements between the positive and negativerails of the DC bus 122. Each vertical grouping of resistors may bereferred to as a string. One or more power grid cooling blowers (e.g.,BL1 and BL2) are normally used to remove heat generated in a string dueto dynamic braking. It is also understood that these contactors(DB1-DB5) can be replaced by solid-state switches like GTO/IGBTs and canbe modulated (like a chopper) to control the effective dynamic brakeresistance.

[0018] As indicated above, prior art Off Highway Vehicles typicallywaste the energy generated from dynamic braking. Attempts to makeproductive use of such energy have been unsatisfactory. For example, onesystem attempts to use energy generated by a traction motor 108 inconnection with an electrolysis cell to generate hydrogen gas as asupplemental fuel source. Among the disadvantages of such a system arethe safe storage of the hydrogen gas and the need to carry water for theelectrolysis process. Still other prior art systems fail to recapturethe dynamic braking energy at all, but rather selectively engage aspecial generator that operates when the associated vehicle travelsdownhill. One of the reasons such a system is unsatisfactory is becauseit fails to recapture existing braking energy and fails to make thecaptured energy available for reuse on board the Off Highway Vehicle.

[0019] Therefore, there is a need for an energy management system andmethod that control when energy is captured and stored, and when suchenergy is regenerated for later use.

SUMMARY OF THE INVENTION

[0020] In one aspect, the invention relates to a hybrid energy offhighway vehicle power storage system and method. The off highway vehiclesystem includes an off highway vehicle having a plurality of vehiclewheels. An off highway vehicle traction motor is associated with one ofthe plurality of vehicle wheels and has a rotatable shaft mechanicallycoupled to the one of the plurality of vehicle wheels. A primary powersource is carried on the off highway vehicle. The off highway vehiclehas an energy management processor. An electric power generator iscarried on the off highway vehicle and is responsive to said processor.The generator is connected to and driven by the primary power source forgenerating and selectively supplying primary electric power to the offhighway vehicle traction motor. The off highway vehicle traction motoris operable in response to the primary electric power to rotate therotatable shaft and to drive the one of the plurality of vehicle wheels.The off highway vehicle traction motor has a dynamic braking mode ofoperation wherein the off highway vehicle traction motor generateselectrical energy in the form of electricity. An electrical energycapture system is carried on the off highway vehicle. The capture systemis responsive to said processor and in electrical communication with theoff highway vehicle traction motor for selectively storing electricalenergy generated in the dynamic braking mode and selectively providingsecondary electric power from said stored electrical energy to thetraction motor to selectively supplement the primary electric power withthe secondary electric power so that said off highway vehicle tractionmotor is operable in response to the primary off highway vehicle powerand the secondary electric power. The processor provides a first controlsignal to the capture system to control the selective storing ofelectrical energy generated in the dynamic braking mode and to controlthe selective providing of secondary electric power to the off highwayvehicle traction motor to supplement the primary electric power. Theprocessor also provides a second control signal to the generator forcontrolling the selective supplying of primary electric power to the offhighway vehicle traction motor.

[0021] In another aspect, the invention relates to a hybrid energy offhighway vehicle system for use in connection with a off highway vehiclefor propelling the off highway vehicle. The system includes a primarypower source carried on the off highway vehicle and an energy managementprocessor. A power converter is driven by the primary power source andselectively provides primary electric power. The power converter isresponsive to the energy management processor. A traction bus is coupledto the power converter and carries the primary electric power. An offhighway vehicle traction system is coupled to the traction bus. Thetraction system has a motoring mode and a dynamic braking mode. Thetraction system propels the off highway vehicle in response to theprimary electric power in the motoring mode and generates electricalenergy in the dynamic braking mode. An electrical energy storage systemis carried on the off highway vehicle and is responsive to theprocessor. The electrical energy storage system is coupled to thetraction bus and selectively captures electrical energy generated by theoff highway vehicle traction system in the dynamic braking mode. Thestorage system selectively transfers the captured electrical energy assecondary electric power to the off highway vehicle traction system toaugment the primary electric power in the motoring mode. The off highwayvehicle traction system propels the off highway vehicle in response tothe secondary electric power. The processor provides a first controlsignal to the electrical energy storage system to control the selectivestoring of electrical energy generated in the dynamic braking mode andto control the selective providing of secondary electric power to theoff highway vehicle traction motor to supplement the primary electricpower, and provides a second control signal to the power converter forcontrolling the selective supplying of primary electric power to the offhighway vehicle traction motor.

[0022] In yet another aspect, the invention relates to an electricalenergy capture system for use in connection with a hybrid energy offhighway vehicle system of an off highway vehicle. The hybrid energy offhighway vehicle system includes an off highway vehicle, a primary powersource, an vehicle electric generator connected to and driven by theprimary power source for selectively supplying primary electric power,and an off highway vehicle traction motor propelling the off highwayvehicle in response to the primary electric power. The off highwayvehicle traction motor has a dynamic braking mode of operationgenerating electrical energy. The electrical energy capture systemincludes an energy management processor carried on the off highwayvehicle. An electrical energy storage device is carried on the offhighway vehicle and is in electrical communication with the off highwayvehicle traction motor. The storage device is responsive to theprocessor, selectively stores electrical energy generated in the dynamicbraking mode, and selectively provides secondary electric power fromsaid stored electricity electrical energy to the off highway vehicletraction motor. The off highway vehicle traction motor is responsive tothe secondary electric power. The processor provides a first controlsignal to the electrical energy storage device to control the selectivestoring of the electrical energy generated in the dynamic braking mode,and to control the selective providing of secondary electric power tothe off highway vehicle traction motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1A is a block diagram of a prior art Off Highway Vehicle.

[0024]FIG. 1B is an electrical schematic of a prior art ACdiesel-electric Off Highway Vehicle.

[0025]FIG. 2 is a block diagram of one embodiment of hybrid energy OffHighway Vehicle system.

[0026]FIG. 3 is a block diagram of one embodiment of hybrid energy OffHighway Vehicle system configured with a fuel cell and a load vehicle.

[0027]FIG. 4 is a block diagram illustrating one embodiment of an energystorage and generation system suitable for use in connection with hybridenergy Off Highway Vehicle system.

[0028]FIG. 5 is a block diagram illustrating an energy storage andgeneration system suitable for use in a hybrid energy Off HighwayVehicle system, including an energy management system for controllingthe storage and regeneration of energy.

[0029] FIGS. 6A-6D are timing diagrams that illustrate one embodiment ofan energy management system for controlling the storage and regenerationof energy, including dynamic braking energy.

[0030] FIGS. 7A-7D are timing diagrams that illustrate anotherembodiment energy management system for controlling the storage andregeneration of energy, including dynamic braking energy.

[0031] FIGS. 8A-8E are timing diagrams that illustrate anotherembodiment energy management system for controlling the storage andregeneration of energy, including dynamic braking energy.

[0032] FIGS. 9A-9G are electrical schematics illustrating severalembodiments of an electrical system suitable for use in connection witha hybrid energy vehicle.

[0033] FIGS. 10A-10C are electrical schematics illustrating additionalembodiments of an electrical system suitable for use in connection witha hybrid energy vehicle.

[0034]FIG. 11 is an electrical schematic that illustrates one embodimentof connecting electrical storage elements.

[0035]FIG. 12 is a flow chart that illustrates one method of operating ahybrid energy Off Highway Vehicle system.

[0036] Corresponding reference characters and designations generallyindicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION OF ASPECTS OF THE INVENTION

[0037]FIG. 2 is a block diagram of one embodiment of a hybrid energy OffHighway Vehicle system 200. In this embodiment, the hybrid energy OffHighway Vehicle system preferably captures and regenerates at least aportion of the dynamic braking electric energy generated when thevehicle traction motors operate in a dynamic braking mode.

[0038] The Off Highway Vehicle system includes an Off Highway Vehicle200 having a primary energy source 104. In some embodiments, a powerconverter is driven by the primary energy source 102 and providesprimary electric power. A traction bus 122 is coupled to the powerconverter and carries the primary electric power. A traction drive 108is coupled to the traction bus 122. The traction drive 108 has amotoring mode in which the traction drive is responsive to the primaryelectric power for propelling the Off Highway Vehicle 200. The tractiondrive 108 has a dynamic braking mode of operation wherein the tractiondrive generates dynamic braking electrical energy. An energy managementsystem 206 comprises an energy management processor (not shown). Theenergy management system 206 determines a power storage parameter and apower transfer parameter. An energy capture and storage system 204 isresponsive to the energy management system 206. The energy capture andstorage system 204 selectively stores electrical energy as a function ofthe power storage parameter. The energy capture and storage system 204selectively supplies secondary electric power from the electrical energystored therein as a function of the power transfer parameter.

[0039] In one embodiment, the energy capture and storage system 204selectively receives electrical power generated during the dynamicbraking mode of operation and stores it for later regeneration and use.In the alternative or in addition to receiving and storing dynamicbraking power, energy capture and storage system 204 can also beconstructed and arranged to receive and store power from other sources.For example, excess prime mover power from primary energy source 104 canbe transferred and stored. Similarly, when two or more Off HighwayVehicles 200 operate in tandem and are electrically coupled, excesspower from one of the Off Highway Vehicles can be transferred and storedin energy capture and storage system 204. Also, a separate primaryenergy source 102 (e.g., diesel generator, fuel cell, trolley line,etc.) can be used to supply a charging voltage (e.g., a constantcharging voltage) to energy capture and storage system 204. Stillanother source of charging is an optional off-vehicle charging source220. For example, energy capture and storage system 204 can be chargedby external charging source 220 such as a battery charger.

[0040] The energy capture and storage system 204 preferably includes atleast one of the following storage subsystems for storing the electricalenergy generated during the dynamic braking mode: a battery subsystem, aflywheel subsystem, an ultra-capacitor subsystem, and a fuel cell fuelgenerator (not shown). Other storage subsystems are possible.Ultra-capacitors are available from Maxwell Technologies. These storagesubsystems may be used separately or in combination. When used incombination, these storage subsystems can provide synergistic benefitsnot realized with the use of a single energy storage subsystem. Aflywheel subsystem, for example, typically stores energy relatively fastbut may be relatively limited in its total energy storage capacity. Abattery subsystem, on the other hand, often stores energy relativelyslowly but can be constructed to provide a relatively large totalstorage capacity. Hence, a flywheel subsystem may be combined with abattery subsystem wherein the flywheel subsystem captures the dynamicbraking energy that cannot be timely captured by the battery subsystem.The energy thus stored in the flywheel subsystem may be thereafter usedto charge the battery. Accordingly, the overall capture and storagecapabilities are preferably extended beyond the limits of either aflywheel subsystem or a battery subsystem operating alone. Suchsynergies can be extended to combinations of other storage subsystems,such as a battery and ultra-capacitor in combination where theultra-capacitor supplies the peak demand needs. In the case where theprimary energy source 102 is a fuel cell, the energy capture and storagesystem 204 may include an electrolysis system that generates hydrogenfrom the fuel cell wastewater. The stored hydrogen is provided to thefuel cell as an energy source for providing primary or secondary power.

[0041] It should be noted at this point that, when a flywheel subsystemis used, a plurality of flywheels is preferably arranged to limit oreliminate the gyroscopic effect each flywheel might otherwise have onthe Off Highway Vehicle and load vehicles. For example, the plurality offlywheels may be arranged on a six-axis basis to greatly reduce oreliminate gyroscopic effects. It should be understood, however, thatreference herein to a flywheel embraces a single flywheel or a pluralityof flywheels.

[0042] Referring still to FIG. 2, energy capture and storage system 204not only captures and stores electric energy generated in the dynamicbraking mode of the Off Highway Vehicle, it also supplies the storedenergy to assist the Off Highway Vehicle effort (i.e., to supplementand/or replace primary energy source power).

[0043] It should be understood that it is common for each Off HighwayVehicle 200 to operate separately from other Off Highway Vehicles.However, two or more Off Highway Vehicles could operate in tandem wherethey are mechanically and/or electrically coupled to operate together.Furthermrore, another optional arrangement includes an Off HighwayVehicle that is mechanically coupled to a load vehicle. While FIG. 2illustrates a single Off Highway Vehicle, FIG. 3 illustrates an OffHighway Vehicle 200 operating in a tandem arrangement with optional loadvehicle 300. Load vehicle 300 may be a passive vehicle that is pulled orpushed by the Off Highway Vehicle 200 or optionally may include aplurality of load vehicle traction motors 308 that provide tractiveeffort to load vehicle wheels 318. The electrical power stored in energycapture and storage 204 may be selectively supplied (e.g., via tandemtraction bus 314) to the load vehicle traction motors 308 via loadvehicle traction bus 312. Thus, during times of increased demand, loadvehicle traction motors 308 augment the tractive power provided by OffHighway Vehicle traction motors 108. As another example, during timeswhen it is not possible to store more energy from dynamic braking (e.g.,energy storage system 204 is charged to capacity), efficiencyconsiderations may suggest that load vehicle traction motors 308 alsoaugment Off Highway Vehicle traction motors 108.

[0044] It should be appreciated that when energy capture and storagesystem 204 drives load vehicle traction motors 308, additional circuitrywill likely be required. For example, if energy capture and storagesystem 204 comprises a battery storing and providing a DC voltage, oneor more inverter drives 106 may be used to convert the DC voltage to aform suitable for use by the load vehicle traction motors 308. Suchdrives are preferably operationally similar to those associated with theOff Highway Vehicle.

[0045] Rather than, or in addition to, using the electrical power storedin energy capture and storage 204 for powering load vehicle tractionmotors 308, such stored energy may also be used to augment theelectrical power supplied to Off Highway Vehicle traction motors 108(e.g., via line 212).

[0046] Other configurations are also possible. For example, the OffHighway Vehicle itself may be configured, either during manufacturing oras part of a retrofit program, to capture, store, and regenerate excesselectrical energy, such as dynamic braking energy, excess primary energysource power or excess trolley line power. In another embodiment, anenergy capture and storage subsystem 306 may be located on some or allof the load vehicles attached to the Off Highway Vehicle. FIG. 3illustrates a load vehicle 300 equipped with a load vehicle energycapture and storage system 306 which receives load vehicle dynamicbraking power from load vehicle traction motor 308 via bus 312 duringdynamic braking. Such a load vehicle 300 may optionally include separatetraction motors 308. In each of the foregoing embodiments, the loadvehicle energy capture and storage subsystem 306 can include one or moreof the subsystems previously described.

[0047] When a separate load vehicle 300 is used, the load vehicle 300and the Off Highway Vehicle 200 are preferably mechanically coupled viamechanical linkage 316 and electrically coupled via tandem traction bus314 such that dynamic braking energy from the Off Highway Vehicletraction motors 108 and/or from optional load vehicle traction motors308 is stored in energy capture and storage system 206 on board the OffHighway Vehicle and/or is stored in load vehicle capture and storagesystem 306 on the load vehicle 300. During motoring operations, thestored energy in the energy capture and storage system in one or theother or both the Off Highway Vehicle 200 and the load vehicle 300 isselectively used to propel Off Highway Vehicle traction motors 108and/or optional load vehicle traction motors 308. Similarly, when theOff Highway Vehicle primary power source 102 produces more power thanrequired for motoring, the excess prime mover power can be stored inenergy capture and storage 204 and or load vehicle energy capture andstorage 306 for later use.

[0048] If load vehicle 300 is not electrically coupled to the OffHighway Vehicle (other than for standard control signals), the optionaltraction motors 308 on the load vehicle 300 can also be used in anautonomous fashion to provide dynamic braking energy to be stored inenergy capture and storage 306 for later use. One advantage of such aconfiguration is that load vehicle 202 can be coupled to a wide varietyof Off Highway Vehicles.

[0049] It should be appreciated that when load vehicle traction motors308 operate in a dynamic braking mode, various reasons may counselagainst storing the dynamic braking energy in energy capture and storage204 and/or 306 (e.g., the storage may be full). Thus, it is preferablethat some or all of the dynamic braking energy generated by the loadvehicle traction motors 308 be dissipated by grids 310 associated withload vehicle 300, or transferred to Off Highway Vehicle 200 to bedissipated by grids 110 (e.g., via tandem traction bus 316).

[0050] It should also be appreciated that load vehicle energy captureand storage system 306 may be charged from an external charging source326 when such a charging source is available.

[0051] The embodiment of FIG. 3 will be further described in terms ofone possible operational example. It is to be understood that thisoperational example does not limit the invention. The Off HighwayVehicle system 200 is configured in tandem including an Off HighwayVehicle 200 and a load vehicle 300. Tractive power for the Off HighwayVehicle 200 is supplied by a plurality of Off Highway Vehicle tractionmotors 108. In one embodiment, the Off Highway Vehicle 200 has fourwheels 109, each pair corresponds to an axle pair as depicted as anoptional embodiment of FIG. 3 as 109A and 109B. Each wheel 109A and 109Bincludes a separate Off Highway Vehicle traction motor 108A and 108B,and each traction motor 108A and 108B is an AC traction motor. In oneembodiment, each of the two rear wheels 109A has a separate Off HighwayVehicle traction motor 108A and operates as pair of wheels 109A on acommon axle, or axle-equivalent (illustrated as a single wheel 109A inFIG. 3). However, the wheels 109A may or may not be actually connectedby a common axle, as such an axle-equivalent. In fact, in oneembodiment, each wheel 109 is mount by a separate half-axle. The OffHighway Vehicle 200 includes a primary energy source 102 that drives anelectrical power system. In one embodiment, the primary energy source isa diesel engine drives an alternator/rectifier 104 that comprises asource of prime mover electrical power (sometimes referred to astraction power or primary power). In this particular embodiment, theprime mover electrical power is DC power that is converted to AC powerfor use by the traction motors. More specifically, one or more inverters(e.g., inverter 106) receive the prime mover electrical power andselectively supply AC power to the plurality of Off Highway Vehicletraction motors 108 to propel the Off Highway Vehicle. In anotherembodiment, the primary energy source 102 is a fuel cell. The fuel cellgenerates DC prime mover power and selectively supplies the DC primarymover power to a DC-to-DC converter 302 as shown in FIG. 3. In yetanother embodiment, the Off Highway Vehicle 200 may utilize a trolleyline (not shown) as the primary energy source, or as a secondary energysource that supplements the primary energy source when the Off HighwayVehicle is traversing an inclined travel path, e.g., trolley assist.Thus, Off Highway Vehicle traction motors 108 propel the Off HighwayVehicle in response to the prime mover electrical power.

[0052] Each of the plurality of Off Highway Vehicle traction motors 108is preferably operable in at least two operating modes, a motoring modeand a dynamic braking mode. In the motoring mode, the Off HighwayVehicle traction motors 108 receive electrical power (e.g., prime moverelectrical power via inverters) to propel the Off Highway Vehicle 200.As described elsewhere herein, when operating in the dynamic brakingmode, the traction motors 108 generate electricity. In the embodiment ofFIG. 3, load vehicle 300 is constructed and arranged to selectivelycapture and store a portion of the electricity generated by the tractionmotors 308 and/or 108 during dynamic braking operations. This isaccomplished by energy capture and storage system 204 and/or 306. Thecaptured and stored electricity is selectively used to provide asecondary source of electric power. This secondary source of electricpower may be used to selectively supplement or replace the prime moverelectrical power (e.g., to help drive one or more Off Highway Vehicletraction motors 108) and/or to drive one or more load vehicle tractionmotors 308. In the latter case, load vehicle traction motors 308 and OffHighway Vehicle traction motors 108 cooperate to propel the tandem OffHighway Vehicle 200 and load vehicle 300.

[0053] Advantageously, load vehicle energy capture and storage 306 canstore dynamic braking energy without any electrical power transferconnection with the primary Off Highway Vehicle. In other words, energycapture and storage 306 can be charged without an electrical couplingsuch as tandem traction bus 314. This is accomplished by operating theOff Highway Vehicle primary power source 320 to provide motoring powerto Off Highway Vehicle traction motors 308 while operating load vehicle300 in a dynamic braking mode. For example, the Off Highway Vehicleprimary power source 102 may be operated at a relatively high powersetting while load vehicle traction motors 308 are configured fordynamic braking. Energy from the dynamic braking process can be used tocharge energy capture and storage 306. Thereafter, the stored energy canbe used to power load vehicle traction motors 308 to provide additionalmotoring power to the tandem Off Highway Vehicle 200 and load vehicle300.

[0054] Referring again to FIG. 3 is another optional embodiment ofhybrid energy Off Highway Vehicle system 300 configured with a fuel cellwith a separate load vehicle. This embodiment includes a fuel cell asprimary power source 102 that drives DC-to-DC converter 302. Converter302 provides DC power to inverter that provides primary tractive power.In another embodiment, where the traction motor 108 is a DC tractionmotor, the converter may provide tractive DC power directly to the DCtraction motor 108 via traction bus 112.

[0055] Referring again to FIG. 3, another optional embodiment includes aload vehicle configured with a load vehicle power source 320. Loadvehicle power source could be any type of power source as describedabove for the Off Highway Vehicle 200. In one embodiment, load vehiclepower source 320 is a fuel cell that generates a constant source of DCelectrical energy. The DC electrical energy that is generated by thefuel cell is converted by a DC-to-DC converter 322 and provided to anInverter 324 for the provision of load vehicle primary power. In thisembodiment, load vehicle primary power may be provided by load vehiclebus 312 to the load vehicle traction motor 308, to the Off HighwayVehicle traction motors 108, to load vehicle energy capture and storagesystem 306, or to Off Highway Vehicle energy capture and storage system204. In this embodiment, the load vehicle power source 320, the powerconverter 322, the converter 324 and/or the load vehicle energy captureand storage system 306 may be operable in response to a load vehicleenergy management system (not shown) or to the energy management system206 of the coupled Off Highway Vehicle via a energy managementcommunication link 328. Such an energy management communication link 328may be a wired communication link or a wireless communication link.

[0056]FIG. 4 is a system-level block diagram that illustrates aspects ofone embodiment of the energy storage and generation system. Inparticular, FIG. 4 illustrates an energy storage and generation system400 suitable for use with a hybrid energy Off Highway Vehicle system,such as hybrid energy Off Highway Vehicle system 200 or load vehiclesystem 300 (FIGS. 3). Such an energy storage and generation system 400could be implemented, for example, as part of a separate load vehicle(e.g., FIGS. 2 and 3) and/or incorporated into an Off Highway Vehicle.

[0057] As illustrated in FIG. 4, a primary energy source 102 drives aprime mover power source 104 (e.g., an alternator/rectifier converter).The prime mover power source 104 preferably supplies DC power to aninverter 106 that provides three-phase AC power to a Off Highway Vehicletraction motor 108. It should be understood, however, that the system400 illustrated in FIG. 4 can be modified to operate with DC tractionmotors as well. Preferably, there is a plurality of traction motors 108,e.g., one per traction wheel 109. In other words, each Off HighwayVehicle traction motor preferably includes a rotatable shaft coupled tothe associated wheel 109 for providing tractive power to the associatedwheel 109. Thus, each Off Highway Vehicle traction motor 108 providesthe necessary motoring force to an associated wheel 109 to cause the OffHighway Vehicle 200 to move. One arrangement includes a single wheel 109on the Off Highway Vehicle to be equipped with a single traction motor108. Another embodiment is for two wheels 109 on opposing sides of thevehicle acting as an axle-equivalent, each equipped with a separatetraction motor 108.

[0058] When traction motors 108 are operated in a dynamic braking mode,at least a portion of the generated electrical power is routed to anenergy storage medium such as energy storage 204. To the extent thatenergy storage 204 is unable to receive and/or store all of the dynamicbraking energy, the excess energy is routed to braking grids 110 fordissipation as heat energy. Also, during periods when primary powersource 102 is being operated such that it provides more energy thanneeded to drive traction motors 108, the excess capacity (also referredto as excess prime mover electric power) may be optionally stored inenergy storage 204. Accordingly, energy storage 204 can be charged attimes other than when traction motors 108 are operating in the dynamicbraking mode. This aspect of the system is illustrated in FIG. 4 by adashed line 402.

[0059] The energy storage 204 of FIG. 4 is preferably constructed andarranged to selectively augment the power provided to traction motors108 or, optionally, to power separate traction motors 308 associated theload vehicle 300. Such power may be referred to as secondary electricpower and is derived from the electrical energy stored in energy storage204. Thus, the system 400 illustrated in FIG. 4 is suitable for use inconnection with an Off Highway Vehicle having an on-board energy captureand storage 204 and/or with a separate load vehicle 300 equipped with aload vehicle energy capture and storage 306.

[0060]FIG. 5 is a block diagram that illustrates aspects of oneembodiment of an energy storage and generation system 500 suitable foruse with a hybrid energy Off Highway Vehicle system. The system 500includes an energy management system 206 for controlling the storage andregeneration of energy. Therefore, although FIG. 5 is generallydescribed with respect to an Off Highway Vehicle system, the energymanagement system 500 illustrated therein is not to be considered aslimited to Off Highway Vehicle applications.

[0061] Referring still to the exemplary embodiment illustrated in FIG.5, system 500 preferably operates in the same general manner as system400 of FIG. 4; the energy management system 206 provides additionalintelligent control functions. FIG. 5 also illustrates an optionalenergy source 504 that is preferably controlled by the energy managementsystem 206. The optional energy source 504 may be a second energy source(e.g., another Off Highway Vehicle operating in tandem with the primaryOff Highway Vehicle) or a completely separate power source (e.g.,trolley line, or a wayside power source such as a battery charger) forcharging energy storage 204. In one embodiment, such a separate chargingpower source includes an electrical power station for charging an energystorage medium associated with a separate load vehicle (e.g., vehicle202 of FIG. 2) while stationary, or a system for charging the energystorage medium while the load vehicle is in motion. In one embodiment,optional energy source 504 is connected to a traction bus (notillustrated in FIG. 5) that also lo carries primary electric power fromprime mover power source 104.

[0062] As illustrated, the energy management system 206 preferablyincludes an energy management processor 506, a database 508, and aposition identification system 510, such as, for example, a globalpositioning satellite system receiver (GPS) 510. The energy managementprocessor 506 determines present and anticipated Off Highway Vehicleposition information via the position identification system 510. In oneembodiment, energy management processor 506 uses this positioninformation to locate data in the database 508 regarding present and/oranticipated travel path topographic and profile conditions, sometimesreferred to as travel path situation information. Such travel pathsituation information may include, for example, travel path grade,travel path elevation (e.g., height above mean sea level), travel pathcurve data, speed limit information, and the like. In the case of alocomotive off highway vehicle, the travel path and characteristics arethose of a railroad track. It is to be understood that such databaseinformation could be provided by a variety of sources including: anonboard database associated with processor 510, a communication system(e.g., a wireless communication system) providing the information from acentral source, manual operator input(s), via one or more travel pathsignaling devices, a combination of such sources, and the like. Finally,other vehicle information such as, the size and weight of the vehicle, apower capacity associated with the prime mover, efficiency ratings,present and anticipated speed, present and anticipated electrical load,and so on may also be included in a database (or supplied in real ornear real time) and used by energy management processor 506.

[0063] It should be appreciated that, in an alternative embodiment,energy management system 206 could be configured to determine powerstorage and transfer requirements associated with energy storage 204 ina static fashion. For example, energy management processor 506 could bepreprogrammed with any of the above information, or could use look-uptables based on past operating experience (e.g., when the vehiclereaches a certain point, it is nearly always necessary to storeadditional energy to meet an upcoming demand).

[0064] The energy management processor 506 preferably uses the presentand/or upcoming travel path situation information, along with OffHighway Vehicle status information, to determine power storage and powertransfer requirements. Energy management processor 506 also determinespossible energy storage opportunities based on the present and futuretravel path situation information. For example, based on the travel pathprofile information, energy management processor 506 may determine thatit is more efficient to completely use all of the stored energy, eventhough present demand is low, because a dynamic braking region is comingup (or because the Off Highway Vehicle is behind schedule and isattempting to make up time). In this way, the energy management system206 improves efficiency by accounting for the stored energy before thenext charging region is encountered. As another example, energymanagement processor 506 may determine not to use stored energy, despitepresent demand, if a heavier demand is soon to be encountered in thetravel path.

[0065] Advantageously, energy management system 206 may also beconfigured to interface with primary energy source controls. Also, asillustrated in FIG. 5, energy storage 204 may be configured to providean intelligent control interface with energy management system 206.

[0066] In operation, energy management processor 506 determines a powerstorage requirement and a power transfer requirement. Energy storage 204stores electrical energy in response to the power storage requirement.Energy storage 204 provides secondary electric power (e.g. to a tractionbus connected to inverters 106 to assist in motoring) in response to thepower transfer requirement. The secondary electric power is derived fromthe electrical energy stored in energy storage 204.

[0067] As explained above, energy management processor 506 preferablydetermines the power storage requirement based, in part, on a situationparameter indicative of a present and/or anticipated travel pathtopographic characteristic. Energy management processor 506 may alsodetermine the power storage requirement as a function of an amount ofprimary electric power available from the prime mover power source 104.Similarly, energy management processor 506 may determine the powerstorage requirement as function of a present or anticipated amount ofprimary electric power required to propel the Off Highway Vehicle.

[0068] Also, in determining the energy storage requirement, energymanagement. processor 506 preferably considers various parametersrelated to energy storage 204. For example, energy storage 204 will havea storage capacity that is indicative of the amount of power that can bestored therein and/or the amount of power that can be transferred toenergy storage 204 at any given time. Another similar parameter relatesto the amount of secondary electric power that energy storage 204 hasavailable for transfer at a particular time.

[0069] As explained above, system 500 preferably includes a plurality ofsources for charging energy storage 204. These sources include dynamicbraking power, excess prime mover electric power, and external chargingelectric power. Preferably, energy management processor 506 determineswhich of these sources should charge energy storage 204. In oneembodiment, present or anticipated dynamic braking energy is used tocharge energy storage 204, if such dynamic braking energy is available.If dynamic braking energy is not available, either excess prime moverelectric power or external charging electric power is used to chargeenergy storage 204.

[0070] In the embodiment of FIG. 5, energy management processor 506preferably determines the power transfer requirement as a function of ademand for power. In other words, energy storage 204 preferably does notsupply secondary electric power unless traction motors 108 are operatingin a power consumption mode (i.e., a motoring mode, as opposed to adynamic braking mode). In one form, energy management processor 506permits energy storage 204 to supply secondary electric power toinverters 106 until either (a) the demand for power terminates or (b)energy storage 204 is completely depleted. In another form, however,energy management processor 506 considers anticipated power demands andcontrols the supply of secondary electric power from energy storage 204such that sufficient reserve power remains in energy storage 204 toaugment prime mover power source during peak demand periods. This may bereferred to as a “look-ahead” energy management scheme.

[0071] In the look-ahead energy management scheme, energy managementprocessor 506 preferably considers various present and/or anticipatedtravel path situation parameters, such as those discussed above. Inaddition, energy management processor may also consider the amount ofpower stored in energy storage 204, anticipated charging opportunities,and any limitations on the ability to transfer secondary electric powerfrom energy storage 204 to inverters 106.

[0072] FIGS. 6A-D, 7A-D, and 8A-E illustrate, in graphic form, aspectsof three different embodiments of energy management systems, suitablefor use with a hybrid energy vehicle, that could be implemented in asystem such as system 500 of FIG. 5. It should be appreciated that thesefigures are provided for exemplary purposes and that, with the benefitof the present disclosure, other variations are possible. It should alsobe appreciated that the values illustrated in these figures are includedto facilitate a detailed description and should not be considered in alimiting sense. It should be further understood that, the examplesillustrated in these figures relate to a variety of large Off HighwayVehicles, including locomotives, excavators and mine trucks and whichare generally capable of storing the electric energy generated duringthe operation of such vehicles. Some of these vehicles travel a known,repetitive or predictable course during operation. For example, alocomotive travels a known travel path, e.g., the railroad track. SuchOff Highway Vehicles include vehicles using DC and AC traction motordrives and having dynamic braking/retarding capabilities.

[0073] There are four similar charts in each group of figures (FIGS.6A-D, FIGS. 7A-D, and FIGS. 8A-D). The first chart in each group (i.e.,FIGS. 6A, 7A, and 8A) illustrates the required power for both motoringand braking. Thus, the first chart graphically depicts the amount ofpower required by the vehicle. Positive values on the vertical axisrepresent motoring power (horsepower); negative values represent dynamicbraking power. It should be understood that motoring power couldoriginate with the prime mover (e.g., diesel engine, fuel cell or otherprimary energy source), or from stored energy (e.g., in an energystorage medium in a separate vehicle), or from a combination of theprime mover and stored energy. Dynamic braking power could be dissipatedor stored in the energy storage medium.

[0074] The horizontal axis in all charts reflects time in minutes. Thetime basis for each chart in a given figure group are intended to be thesame. It should be understood, however, that other reference bases arepossible.

[0075] The second chart in each group of figures (i.e., FIGS. 6B, 7B,and 8B) reflects theoretical power storage and consumption. Positivevalues reflect the amount of power that, if power were available in theenergy storage medium, could be drawn to assist in motoring. Negativevalues reflect the amount of power that, if storage space remains in theenergy storage medium, could be stored in the medium. The amount ofpower that could be stored or drawn is partially a function of theconverter and storage capabilities of a given vehicle configuration. Forexample, the energy storage medium will have some maximum/finitecapacity. Further, the speed at which the storage medium is able toaccept or supply energy is also limited (e.g., batteries typicallycharge slower than flywheel devices). Other variables also affect energystorage. These variables include, for example, ambient temperature, thesize and length of any interconnect cabling, current and voltage limitson dc-to-dc converters used for battery charging, power ratings for aninverter for a flywheel drive, the charging and discharging rates of abattery, or a motor/shaft limit for a flywheel drive. The second chartassumes that the maximum amount of power that could be transferred to orfrom the energy storage medium at a given time is 500 h.p. Again, itshould be understood that this 500 h.p. limit is included for exemplarypurposes. Hence, the positive and negative limits in any given systemcould vary as a function of ambient conditions, the state and type ofthe energy storage medium, the type and limits of energy conversionequipment used, and the like.

[0076] The third chart in each figure group (i.e., FIGS. 6C, 7C, and 8C)depicts a power transfer associated with the energy storage medium. Inparticular, the third chart illustrates the actual power beingtransferred to and from the energy storage medium versus time. The thirdchart reflects limitations due to the power available for storage, andlimitations due to the present state of charge/storage of the energystorage medium (e.g., the speed of the flywheel, the voltage in anultra-capacitor, the charge in the battery, and the like).

[0077] The fourth chart in each figure group (i.e., FIGS. 6D, 7D, and8D) depicts actual energy stored. In particular, the fourth chartillustrates the energy stored in the energy storage medium at anyparticular instant in time.

[0078] Referring first to FIGS. 6A-D, these figures reflect an energymanagement system that stores energy at the maximum rate possible duringdynamic braking until the energy storage medium is completely full. Inthis embodiment, all energy transfers to the storage medium occur duringdynamic braking. In other words, in the embodiment reflected in FIGS.6A-D, no energy is transferred to the energy storage medium from excessprime mover power available during motoring, or from other energysources. Similarly, energy is discharged, up to the maximum rate,whenever there is a motor demand (limited to and not exceeding theactual demand) until the energy storage medium is completelydischarged/empty. FIGS. 6A-D assume that the energy storage medium iscompletely discharged/empty at time 0.

[0079] Referring now specifically to FIG. 6A, as mentioned above, theexemplary curve identified therein illustrates the power required(utilized) for motoring and dynamic braking. Positive units of powerreflect when motoring power is being applied to the wheels 109 of thevehicle (e.g., one or more traction motors are driving Off HighwayVehicle wheels). Negative units of power reflect power generated bydynamic braking.

[0080]FIG. 6B is an exemplary curve that reflects power transfer limits.Positive values reflect the amount of stored energy that would be usedto assist in the motoring effort, if such energy were available.Negative units reflect the amount of dynamic braking energy that couldbe stored in the energy storage medium if the medium were able to acceptthe full charge available. In the example of FIG. 6B, the energyavailable for storage at any given time is illustrated as being limitedto 500 units (e.g., to horsepower). As explained above, a variety offactors limit the amount of power that can be captured and transferred.Thus, from about 0 to 30 minutes, the Off Highway Vehicle requires lessthan 500 h.p. If stored energy were available, it could be used toprovide all of the motoring power. From about 30 minutes to about 65 or70 minutes, the Off Highway Vehicle requires more than 500 h.p. Thus, ifstored energy were available, it could supply some (e.g., 500 h.p.) butnot all of the motoring power. From about 70 minutes to about 75 minutesor so, the Off Highway Vehicle is in a dynamic braking mode andgenerates less than 500 h.p. of dynamic braking energy. Thus, up to 500h.p. of energy could be transferred to the energy storage medium, if themedium retained sufficient capacity to store the energy. At about 75minutes, the dynamic braking process generates in excess of 500 h.p.Because of power transfer limits, only up to 500 h.p. could betransferred to the energy storage medium (again, assuming that storagecapacity remains); the excess power would be dissipated in the brakinggrids. It should be understood that FIG. 6B does not reflect the actualamount of energy transferred to or from the energy storage medium. Thatinformation is depicted in FIG. 6C. FIG. 6C is reflects the powertransfer to/from the energy storage medium at any given instant of time.The example shown therein assumes that the energy storage medium iscompletely empty at time 0. Therefore, the system cannot transfer anypower from the storage at this time. During a first time period A (fromapproximately 0-70 minutes), the vehicle is motoring (see FIG. 6A) andno power is transferred to or from the energy storage. At the end of thefirst time period A, and for almost 30 minutes thereafter, the vehicleenters a dynamic braking phase (see FIG. 6A). During this time, powerfrom the dynamic braking process is available for storage (see FIG. 6B).

[0081] During a second time period B (from approximately 70-80 minutes),dynamic braking energy is transferred to the energy storage medium atthe maximum rate (e.g., 500 units) until the storage is full. Duringthis time there is no motoring demand to deplete the stored energy.Thereafter, during a third time period C (from approximately 80-105minutes) the storage is full. Consequently, even though the vehicleremains in the dynamic braking mode or is coasting (see FIG. 6A), noenergy is transferred to or from the energy storage medium during timeperiod C.

[0082] During a fourth time period D (from approximately 105-120minutes), the vehicle resumes motoring. Because energy is available inthe energy storage medium, energy is drawn from the storage and used toassist the motoring process. Hence, the curve illustrates that energy isbeing drawn from the energy storage medium during the fourth time periodD.

[0083] At approximately 120 minutes, the motoring phase ceases and,shortly thereafter, another dynamic braking phase begins. This dynamicbraking phase reflects the start of a fifth time period E that lastsfrom approximately 125-145 minutes. As can be appreciated by viewing thecurve during the fifth time period E, when the dynamic braking phaseends, the energy storage medium is not completely charged.

[0084] Shortly before the 150-minute point, a sixth time period F beginswhich lasts from approximately 150-170 minutes. During this time periodand thereafter (see FIG. 6A), the vehicle is motoring. Fromapproximately 150-170 minutes, energy is transferred from the energystorage medium to assist in the motoring process. At approximately 170minutes, however, the energy storage is completely depleted.Accordingly, from approximately 170-200 minutes (the end of the samplewindow), no energy is transferred to or from the energy storage medium.

[0085]FIG. 6D illustrates the energy stored in the energy storage mediumof the exemplary embodiment reflected in FIGS. 6A-D. Recall that in thepresent example, the energy storage medium is assumed to be completelyempty/discharged at time 0. Recall also that the present example assumesan energy management system that only stores energy from dynamicbraking. From approximately 0-70 minutes, the vehicle is motoring and noenergy is transferred to or from the energy storage medium. Fromapproximately 70-80 minutes or so, energy from dynamic braking istransferred to the energy storage medium until it is completely full. Atapproximately 105 minutes, the vehicle begins another motoring phase andenergy is drawn from the energy storage medium until about 120 minutes.At about 125 minutes, energy from dynamic braking is again transferredto the energy storage medium during another dynamic braking phase. Atabout 145 minutes or so, the dynamic braking phase ends and storageceases. At about 150 minutes, energy is drawn from the energy storagemedium to assist in motoring until all of the energy has been depletedat approximately 170 minutes.

[0086] FIGS. 7A-D correspond to an energy management system thatincludes a “look-ahead” or anticipated needs capability. This embodimentapplies particularly when the travel path of the Off Highway Vehicle isknown or is planned. Such a system is unlike the system reflected inFIGS. 6A-D, which simply stores dynamic braking energy when it can, anduses stored energy to assist motoring whenever such stored energy isavailable. The energy management system reflected by the exemplarycurves of FIGS. 7A-D anticipates when the prime mover cannot produce thefull required demand, or when it may be less efficient for the primemover to produce the full required demand. As discussed elsewhereherein, the energy management system can make such determinations basedon, for example, known present position, present energy needs,anticipated future travel path topography, anticipated future energyneeds, present energy storage capacity, anticipated energy storageopportunities, and like considerations. The energy management systemdepicted in FIGS. 7A-D, therefore, preferably prevents the energystorage medium from becoming depleted below a determined minimum levelrequired to meet future demands.

[0087] By way of further example, the system reflected in FIGS. 7A-D ispremised on a Off Highway Vehicle having a primary energy source thathas a “prime mover limit” of 4,000 h.p. Such a limit could exist forvarious factors. For example, the maximum rated output could be 4,000h.p., or operating efficiency considerations may counsel againstoperating the primary power source above 4,000 h.p. It should beunderstood, however, that the system and figures are intended to reflectan exemplary embodiment only, and are presented herein to facilitate adetailed explanation of aspects of an energy management system suitablefor use with off-highway hybrid energy vehicles such as, for example,the Off Highway Vehicle system illustrated in FIG. 2.

[0088] Referring now to FIG. 7A, the exemplary curve illustrated thereindepicts the power required for motoring (positive) and braking(negative). At approximately 180 minutes, the motoring demand exceeds4,000 h.p. Thus, the total demand at that time exceeds the 4,000 h.p.operating constraint for the primary energy source. The “look-ahead”energy management system reflected in FIGS. 7A-D, however, anticipatesthis upcoming need and ensures that sufficient secondary power isavailable from the energy storage medium to fulfill the energy needs.

[0089] One way for the energy management system to accomplish this is tolook ahead (periodically or continuously) to the upcoming travelpath/course profile (e.g., incline/decline, length of incline/decline,and the like) for a given time period (also referred to as a look-aheadwindow). In the example illustrated in FIGS. 7A-D, the energy managementsystem looks ahead 200 minutes and then computes energyneeds/requirements backwards. The system determines that, for a briefperiod beginning at 180 minutes, the primary energy source would requiremore energy than the limit.

[0090]FIG. 7B is similar to FIG. 6B. FIG. 7B, however, also illustratesthe fact that the energy storage medium is empty at time 0 and,therefore, there can be no power transfer from the energy storage mediumunless and until it is charged. FIG. 7B also reflects a look-aheadcapability.

[0091] Comparing FIGS. 6A-D with FIGS. 7A-D, it is apparent how thesystems respectively depicted therein differ. Although the requiredpower is the same in both examples (see FIGS. 6A and 7A), the systemreflected in FIGS. 7A-D prevents complete discharge of the energystorage medium prior to the anticipated need at 180 minutes. Thus, ascan be seen in FIGS. 7C and 7D, prior to the 180 minute point, thesystem briefly stops transferring stored energy to assist in motoring,even though additional stored energy remains available. The additionalenergy is thereafter transferred, beginning at about 180 minutes, toassist the prime mover when the energy demand exceeds 4,000 h.p. Hence,the system effectively reserves some of the stored energy to meetupcoming demands that exceed the desired limit of the prime mover.

[0092] It should be understood and appreciated that the energy availablein the energy storage medium could be used to supplement drivingtraction motors associated with the prime mover, or could also be usedto drive separate traction motors (e.g., on a load vehicle). With thebenefit of the present disclosure, an energy management systemaccommodating a variety of configurations is possible.

[0093] FIGS. 8A-E reflect pertinent aspects of another embodiment of anenergy management system suitable for use in connection with Off HighwayVehicle energy vehicles. The system reflected in FIGS. 8A-E includes acapability to store energy from both dynamic braking and from the primemover or another charging power source. For example, a given powersource may operate most efficiently at a given power setting (e.g.,4,000 h.p.). Thus, it may be more efficient to operate the power sourceat 4,000 h.p. at certain times, even when actual motoring demand fallsbelow that level. In such cases, the excess energy can be transferred toan energy storage medium.

[0094] Thus, comparing FIGS. 8A-D with FIGS. 6A-D and 7A-D, thedifferences between the systems respectively depicted therein areapparent. Referring specifically to FIGS. 8A and 8D, from about 0-70minutes, the motoring requirements (FIG. 8A) are less than the exemplaryoptimal 4,000 h.p. setting. If desirable, the power source could be runat 4,000 h.p. during this time and the energy storage medium could becharged. As illustrated, however, the energy management systemdetermines that, based on the upcoming travel path profile andanticipated dynamic braking period(s), an upcoming dynamic brakingprocess will be able to fully charge the energy storage medium. In otherwords, it is not necessary to operate the primary energy source at 4,000h.p. and store the excess energy in the energy storage medium duringthis time because an upcoming dynamic braking phase will supply enoughenergy to fully charge the storage medium. It should be understood thatthe system could also be designed in other ways. For example, in anotherconfiguration the system always seeks to charge the storage mediumwhenever excess energy could be made available.

[0095] At approximately 180 minutes, power demands will exceed 4,000h.p. Thus, shortly before that time (while motoring demand is less than4,000 h.p.), the primary energy source can be operated at 4,000 h.p.,with the excess energy used to charge the energy storage medium toensure sufficient energy is available to meet the demand at 180 minutes.Thus, unlike the systems reflected in FIGS. 6D and 7D, the systemreflected in FIG. 8D provides that, for a brief period prior to 180minutes, energy is transferred to the energy storage medium from theprime mover, even though the vehicle is motoring (not braking).

[0096]FIG. 8E illustrates one way that the energy management system canimplement the look-ahead capability to control energy storage andtransfer in anticipation of future demands. FIG. 8E assumes a systemhaving a 200 minute look-ahead window. Such a look-ahead window ischosen to facilitate an explanation of the system and should not beviewed in a limiting sense. Beginning at the end of the window (200minutes), the system determines the power/energy demands at any givenpoint in time. If the determined demand exceeds the prime mover'scapacity or limit, the system continues back and determinesopportunities when energy can be stored, in advance of the determinedexcess demand period, and ensures that sufficient energy is storedduring such opportunities.

[0097] Although FIGS. 6A-D, 7A-D, and 8A-E have been separatelydescribed, it should be understood that the systems reflected thereincould be embodied in a single energy management system. Further, thelook-ahead energy storage and transfer capability described above couldbe accomplished dynamically or in advance. For example, in one form, anenergy management processor (see FIG. 5) is programmed to compare thevehicle's present position with upcoming travel path/coursecharacteristics in real or near real time. Based on such dynamicdeterminations, the processor then determines how to best manage theenergy capture and storage capabilities associated with the vehicle in amanner similar to that described above with respect to FIGS. 7A-D and8A-E. In another form, such determinations are made in advance. Forexample, an off-vehicle planning computer may be used to plan a routeand determine energy storage and transfer opportunities based on adatabase of known course information and projected conditions such as,for example, vehicle speed, weather conditions, and the like. Suchpre-planned data would thereafter be used by the energy managementsystem to manage the energy capture and storage process. Look-aheadplanning could also be done based on a route segment or an entire route.In some Off Highway Vehicle applications, such as a mine truck orexcavator, the travel path may be substantially the same on a day-to-daybasis, but may change on a weekly or monthly basis as the mine is workedand the travel path changes to adapt to the mine configuration. In thesecases, look-ahead planning may be changed as changes to the travel pathoccur.

[0098] It should further be understood that the energy management systemand methods described herein may be put into practice with a variety ofvehicle configurations. The energy management systems and methodsdescribed herein may be employed as part of an Off Highway Vehicle inwhich the energy storage medium is included as part of the vehicleitself. In other embodiments, such systems and methods could bepracticed with a Off Highway Vehicle having a separate load vehicleconfigured to house an external energy capture and storage medium. Asanother example, the energy management systems and methods hereindescribed could be employed with a Off Highway Vehicle having a separateload vehicle that employs its own traction motors. Other possibleembodiments and combinations should be appreciated from the presentdisclosure and need not be recited in additional detail herein.

[0099] FIGS. 9A-9G are electrical schematics illustrating severaldifferent embodiments of an electrical system suitable for use inconnection with a hybrid energy Off Highway Vehicle. In particular, theexemplary embodiments illustrated in these figures relate to a hybridenergy Off Highway Vehicle system. It should be understood that theembodiments illustrated in FIGS. 9A-9G could be incorporated in aplurality of configurations, including those already discussed herein(e.g., a Off Highway Vehicle with a separate load vehicle, a Off HighwayVehicle with a self-contained hybrid energy system, an autonomous loadvehicle, and the like). Other vehicles like off highway dump trucks formining use the same type of configuration using one, two or fourtraction motors, one per each driving wheel 109.

[0100]FIG. 9A illustrates an electrical schematic of a Off HighwayVehicle electrical system having a energy capture and storage mediumsuitable for use in connection with aspects of the systems and methodsdisclosed herein. The particular energy storage element illustrated inFIG. 9A comprises a battery storage 902. The battery storage 902 ispreferably connected directly across the traction bus (DC bus 122). Inthis exemplary embodiment, an auxiliary power drive 904 is alsoconnected directly across DC bus 122. The power for the auxiliaries isderived from DC bus 122, rather than a separate bus.

[0101] It should be appreciated that more than one type of energystorage element may be employed in addition to battery storage 902. Forexample, an optional flywheel storage element 906 can also be connectedin parallel with battery storage 902. The flywheel storage 906 shown inFIG. 9A is preferably powered by an AC motor or generator connected toDC bus 122 via an inverter or converter. Other storage elements such as,for example, capacitor storage devices (including ultra-capacitors) andadditional battery storages (not shown) can also be connected across theDC bus and controlled using choppers and/or converters and the like. Itshould be understood that although battery storage 902 is schematicallyillustrated as a single battery, multiple batteries or battery banks maylikewise be employed.

[0102] In operation, the energy storage elements (e.g., battery storage902 and/or any optional energy storage elements such as flywheel 906)are charged directly during dynamic braking operations. Recall that,during dynamic braking, one or more of the traction motor subsystems(e.g., 124A-124B) operate as generators and supply dynamic brakingelectric power that is carried on DC bus 122. Thus, all or a portion ofthe dynamic braking electric power carried on DC bus 122 may be storedin the energy storage element because the power available on the busexceeds demand. When the power source is motoring, the battery (and anyother optional storage element) is permitted to discharge and provideenergy to DC bus 122 that can be used to assist in driving the tractionmotors. This energy provided by the storage element may be referred toas secondary electric power. Advantageously, because the auxiliaries arealso driven by the same bus in this configuration, the ability to takepower directly from DC bus 122 (or put power back into bus 122) isprovided. This helps to minimize the number of power conversion stagesand associated inefficiencies due to conversion losses. It also reducescosts and complexities.

[0103] In an alternative embodiment, a fuel cell provides all or aportion of the primary power. In this embodiment, the energy storagedevice may include an electrolysis or similar fuel cell energy sourcegeneration. As one example, the energy generated during dynamic brakingpowers electrolysis to create hydrogen from water, one water sourcebeing the waster water created by the fuel cell during prime energygeneration. The generated hydrogen is stored and is used as a fuel forthe primary power source, the fuel cell.

[0104] It should be appreciated that the braking grids may still be usedto dissipate all or a portion of the dynamic braking electric powergenerated during dynamic braking operations. For example, an energymanagement system is preferably used in connection with the systemillustrated in FIG. 9A. Such an energy management system is configuredto control one or more of the following functions: primary energygeneration, energy storage; stored energy usage; and energy dissipationusing the braking grids. It should further be appreciated that thebattery storage (and/or any other optional storage element) mayoptionally be configured to store excess prime mover electric power thatis available on the traction bus.

[0105] Those skilled in the art should appreciate that certaincircumstances preclude the operation of a diesel engine or fuel celloperating as the primary energy source when the Off Highway Vehicleneeds to be moved. For example, the engine or fuel cell may not beoperable. As another example, various rules and concerns may prevent theoperation of a diesel engine inside buildings, yards, maintenancefacilities, mines or tunnels. In such situations, the Off HighwayVehicle may be moved using a fuel cell or stored secondary power.Advantageously, various hybrid energy Off Highway Vehicle configurationsdisclosed herein permit the use of stored power for battery jogoperations directly. For example, the battery storage 902 of FIG. 9A canbe used for battery jog operations. Further, the prior concept ofbattery jog operations suggests a relatively short time period over ashort distance. The various configurations disclosed herein permit jogoperations for much longer time periods and over much longer distances.

[0106]FIG. 9B illustrates a variation of the system of FIG. 9A. Aprimary difference between FIGS. 9A and 9B is that the system shown inFIG. 9B includes chopper circuits DBC1 and DBC2 connected in series withthe braking grids. The chopper circuits DBC1 and DBC2 allow fine controlof power dissipation through the grids that, therefore, provides greatercontrol over the storage elements such as, for example, battery storage902. In one embodiment, chopper circuits DBC1 and DBC2 are controlled byan energy management system (see FIG. 5). It should also be appreciatedthat chopper circuits DBC1 and DBC2, as well as any optional storagedevices added to the circuit (e.g., flywheel storage 906), could also beused to control transient power. In some embodiments, a combination ofdynamic braking contactors and chopper circuits may be utilized.

[0107] In the configuration of FIG. 9A, the dynamic braking contactors(e.g., DB1, DB2) normally only control the dynamic braking grids indiscrete increments. Thus, the power flowing into the grids is also indiscrete increments (assuming a fixed DC voltage). For example, if eachdiscrete increment is 1,000 h.p., the battery storage capability is2,000 h.p., and the braking energy returned is 2,500 h.p., the batterycannot accept all of the braking energy. As such, one string of grids isused to dissipate 1,000 h.p., leaving 1,500 h.p. for storage in thebattery. By adding choppers DBC1, DBC2, the power dissipated in eachgrid string can be more closely controlled, thereby storing more energyin the battery and improving efficiency. In the foregoing example,choppers DBC1 and DBC2 can be operated at complementary 50% duty cyclesso that only 500 h.p. of the braking energy is dissipated in the gridsand 2,000 h.p. is stored in the battery.

[0108]FIG. 9C is an electrical schematic of a Off Highway Vehicleelectrical system illustrating still another configuration forimplementing an energy storage medium. In contrast to the systemsillustrated in FIGS. 9A and 9B, the battery storage 902 of FIG. 9C isconnected to DC bus 122 by way of a dc-to-dc converter 910. Such aconfiguration accommodates a greater degree of variation between DC bus122 voltage and the voltage rating of battery storage 902. Multiplebatteries and/or DC storage elements (e.g., capacitors) could beconnected in a similar manner. Likewise, chopper control, such as thatillustrated in FIG. 9B could be implemented as part of the configurationof FIG. 9C. It should be further understood that the dc-to-dc converter910 may be controlled via an energy management processor (see FIG. 5) aspart of an energy management system and process that controls thestorage and regeneration of energy in the energy storage medium.

[0109] In operation, the electric power carried on DC bus 122 isprovided at a first power level (e.g., a first voltage level). Thedc-to-dc converter 910 is electrically coupled to DC bus 122. Thedc-to-dc converter 910 receives the electric power at the first powerlevel and converts it to a second power level (e.g., a second voltagelevel). In this way, the electric power stored in battery storage 902 issupplied at the second power level. It should be appreciated that thevoltage level on DC bus 122 and the voltage supplied to battery storage902 via dc-to-dc converter 910 may also be at the same power level. Theprovision of dc-to-dc converter 910, however, accommodates variationsbetween these respective power levels.

[0110]FIG. 9D is an electrical schematic of a Off Highway Vehicleelectrical system that is similar to the system shown in FIG. 9C. Onedifference between these systems is that the auxiliary power subsystem904 reflected in FIG. 9D is connected to DC bus 122 via a pair ofdc-to-dc converters 912 and 914. Such a configuration provides theadvantage of allowing the use of existing, lower voltage auxiliarydrives and/or motor drives having low insulation. On the other hand, inthis configuration, the auxiliary power traverses two power conversionstages. It should be understood that although FIG. 9D illustrates theauxiliaries as consuming power all of the time—notregenerating—bi-directional dc-to-dc converters can also be used inconfigurations in which it is desirable to have the auxiliariesregenerate power (see, for example, FIG. 9G). These dc-to-dc converters912 and 914 are preferably controlled via an energy management systemthat controls the storage and regeneration of energy in the energystorage medium.

[0111]FIG. 9E illustrates, in electrical schematic form, still anotherconfiguration of an energy storage medium. Unlike the examplesillustrated in FIGS. 9A-9D, however, the configuration of FIG. 9Eincludes a separate DC battery bus 922. The separate battery bus 922 iselectrically isolated from main DC bus 122 (the traction bus) by adc-to-dc converter 920 (also referred to as a two-stage converter).Accordingly, the power flow between the traction bus (DC bus 122), theenergy storage elements, and the auxiliaries preferably passes throughthe bi-directional dc-to-dc converter 920. In the configuration of FIG.9E, any additional storage elements (e.g., flywheels, capacitors, andthe like) are preferably connected across the DC battery bus 922, ratherthan across the main DC bus 122. The dc-to-dc converter 920 may becontrolled via an energy management system that controls the storage andregeneration of energy in the energy storage medium.

[0112]FIG. 9F reflects a variation of the configuration of FIG. 9E. Inthe configuration of FIG. 9F, any variable voltage storage elements(e.g., capacitors, flywheels, and the like) that are used in addition tobattery 906 are connected directly across main DC bus 122 (the tractionbus). However, battery 906 remains connected across the isolated DCbattery bus 922. Advantageously, in this configuration dc-to-dcconverter 920 matches the voltage level of battery storage 902 butavoids two conversions of large amounts of power for the variablevoltage storage elements. Like the other configurations, theconfiguration of FIG. 9F may be implemented in connection with an energymanagement system that oversees and controls the storage andregeneration of energy in the energy storage medium.

[0113]FIG. 9G reflects a variation of the configuration of FIG. 9F inwhich only the auxiliaries are connected to a separate auxiliary bus 930through two-stage converter 920. Accordingly, electric power carried onDC bus 122 is provided at a first power level and power carried on theauxiliary bus 930 is provided at a second power level. The first andsecond power levels may or may not be the same.

[0114] FIGS. 10A-10C are electrical schematics that illustrateadditional embodiments, including embodiments particularly suited formodifying existing AC Off Highway Vehicles. It should be understood,however, that the configurations illustrated and described with respectto FIGS. 10A-10C are not limited to retrofitting existing Off HighwayVehicles.

[0115]FIG. 10A illustrates a variation of the embodiment illustrated inFIG. 9C. The embodiment of FIG. 10A uses only battery storage devicesand does not include a non-battery storage, such as optional flywheelstorage 906. In particular, FIG. 10A illustrates an embodiment having aconverter 1006 (e.g., a dc-to-dc converter) connected across DC bus 122.A battery storage element 1002 is connected to the converter 1006.Additional converters and battery storage elements may be added to thisconfiguration in parallel. For example, another converter 1008 may beconnected across DC bus 122 to charge another battery storage element1004. One of the advantages of the configuration of FIG. 10A is that itfacilitates the use of multiple batteries (or battery banks) havingdifferent voltages and/or charging rates.

[0116] In certain embodiments, power transfer between energy storagedevices is facilitated. The configuration of FIG. 10A, for instance,allows for energy transfer between batteries 1002 and 1004 via the DCbus 122. For example, if during motoring operations, the primary powersource supplies 2,000 h.p. of power to the dc traction bus, the tractionmotors consume 2,000 h.p., and battery 1002 supplies 100 h.p. to thetraction bus (via converter 1006), the excess 100 h.p. is effectivelytransferred from battery 1002 to battery 1004 (less any normal losses).

[0117] The configuration illustrated in FIG. 10B is similar to that ofFIG. 10A, except that it uses a plurality of converters (e.g.,converters 1006, 1008) connected to the DC bus 122 to supply a commonbattery 1020 (or a common battery bank). One of the advantages of theconfiguration of FIG. 10B is that it allows the use of relativelysmaller converters. This may be particularly advantageous whenretrofitting an existing Off Highway Vehicle that already has oneconverter. A similar advantage of this configuration is that it allowsthe use of higher capacity batteries. Still another advantage of theconfiguration of FIG. 10B is that it permits certain phase shiftingoperations, thereby reducing the ripple current in the battery andallowing the use of smaller inductors (not shown). For example, ifconverters 1006 and 1008 are operated at 1,000 Hz, 50% duty cycles, andthe duty cycles are selected such that converter 1006 is on whileconverter 1008 is off, the converter effect is as if a single converteris operating at 2,000 Hz, which allows the use of smaller inductors.

[0118]FIG. 10C an electrical schematic illustrating another embodimentthat is particularly well suited for retrofitting an existing OffHighway Vehicle to operate as a hybrid energy Off Highway Vehicle. Theconfiguration of FIG. 10C uses a double set of converters 1006, 1030 andone or more batteries 1020 (of the same or different voltage levels). Anadvantage of the system depicted in FIG. 10C is that the battery 1020can be at a higher voltage level than the DC bus 122. For example, ifthe converters 1006, 1008 illustrated in FIGS. 10A and 10B are typicaltwo quadrant converters, they will also have freewheeling diodesassociated therewith (not illustrated). If the voltage of battery 1002,1004 (FIG. 10A), or 1020 (FIG. 10B) exceeds the DC bus voltage, thebattery will discharge through the freewheeling diode. A doubleconverter, such as that illustrated in FIG. 10C, avoids this situation.One advantage of this capability is that the voltage level on the DC buscan be modulated to control power to the dynamic braking gridsindependently.

[0119]FIG. 11 is an electrical schematic that illustrates one way ofconnecting electrical storage elements. In particular, FIG. 11illustrates an electrical schematic of a system that may be used forretrofitting a prior art Off Highway Vehicle to operate as a hybridenergy Off Highway Vehicle, or for installing a hybrid energy system aspart of the original equipment during the manufacturing process. Theembodiment illustrated assumes an AC diesel-electric Off Highway Vehiclewith four wheels, a pair of wheels located on two axle-equivalents. Twowheels 109 of a single axle-equivalent are driven by individual tractionmotor subsystems. However, in other embodiments all four wheels 109A and109B of the two axle-equivalents may be driven by four traction motorsubsystems, or any number of traction motors are envisioned consistentwith the current invention. For instance, while not commonplace for OffHighway Vehicles would be to have two wheels 109A on a single axle witha single traction motor subsystem for the single axle two wheelarrangement.

[0120] Typically, the primary energy source has extra capability (e.g.,power capacity) available in the majority of operating conditions. Suchextra capability may be due to lower actual ambient conditions, ascompared with the design criteria. For example, some Off HighwayVehicles are designed to operate in ambient temperatures of up to 60degrees Celsius, which is well above typical operating conditions.Considerations other than thermal conditions may also result in extracapacity during significant operating periods. In a typical Off HighwayVehicle, for instance, the use of all of the traction motors may only berequired for low speed and when the Off Highway Vehicle operates in anadhesion limited situation (poor tractive conditions). In such case, theweight on the driven wheels 109 determines the pulling power/tractiveeffort. Hence, all available wheel/motors need to be driven to obtainmaximum tractive effort. This can be especially true if the Off HighwayVehicle is heavily loaded during poor tractive conditions (snow, mud, orwet). Such conditions may normally be present for only a fraction of theoperating time. During the majority of the operating time, all of thetraction motors/inverters are not fully utilized to supply tractiveeffort. Thus, for example, when retrofitting an existing prior art OffHighway Vehicle, or manufacturing a new Off Highway Vehicle, it ispossible to take advantage of this partial underutilization of thetraction motors/inverters.

[0121] By way of a specific example, the embodiment of FIG. 11 isconfigured such that one of the two traction motor subsystems isconnected to the energy storage element 1102, through a transfer switch1104 and a plurality of inductors 1110. More particularly, the tractionmotor subsystem 124B includes an inverter 106B and a traction motor1108B. Such a configuration is suited for retrofitting a single wheel109 of an existing prior art Off Highway Vehicle. It should beunderstood that retrofitting a typical prior art Off Highway Vehiclerequires the addition of power conversion equipment and associatedcooling devices. The space available for installing the retrofitequipment, however, is generally limited. Therefore, one of theadvantages of the “single-wheel” configuration of FIG. 11 is that ittends to minimize impacts and makes retrofitting a more viable option.Similar advantages, however, may also be enjoyed when the hybrid energysystem is installed as original equipment during manufacturing.

[0122] The transfer switch 1104 preferably comprises a three-phase setof contactors or a set of motorized contacts (e.g., bus bars) thatconnect inverter 106B to traction motor 1108B when all of the wheels109A and 109B are needed, and connects inverter 106B to inductors 1110and battery 1102 when battery charging or discharging is desired. Thus,transfer switch 1104 has a first connection state and a secondconnection state. In the first connection state, transfer switch 1104connects inverter 106B to traction motor 1108B. In the second connectionstate, transfer switch connects inverter 106B to battery 1102.

[0123] Transfer switch 1104 is preferably controlled by a switchcontroller 1120. In one form, the switch controller 1120 is a manualoperator-controlled switch that places transfer switch 1104 into thefirst or the second connection state. In another form, the switchcontroller reflects control logic that controls the connection state oftransfer switch 1104 in accordance with one operating scheme. Table I(below) is indicative of one such operating scheme. Other schemes arepossible.

[0124] Although FIG. 11 illustrates a three-phase connection betweenbattery 1102 and transfer switch 1104, it is not necessary that allthree phases be used. For example, if the power requirement isrelatively low, only one or two phases may be used. Similarly, threeseparate batteries could be independently connected (one to each phase),or one large battery could be connected to two phases, with a relativelysmaller battery connected to the third phase. Further, power transferbetween multiple batteries having different voltage potentials and/orcapacities is also possible.

[0125] The configuration of FIG. 11 is especially advantageous in thecontext of retrofitting existing Off Highway Vehicles because transferswitch 1104 is believed to be much less expensive than adding additionalinverters and/or dc-to-dc converters. Such advantage, however, is notlimited to the retrofit context. Also, it should be understood that theconfiguration of FIG. 11 is not limited to a single inverter pertransfer switch configuration.

[0126]FIG. 11 further illustrates an optional charging source 1130 thatmay be electrically connected to DC traction bus 122. The chargingsource 1130 may be, for example, another charging energy source or anexternal charger, such as that discussed in connection with FIG. 5.

[0127] The general operation of the configuration of FIG. 11 will bedescribed by reference to the connection states of transfer switch 1104.When transfer switch 1104 is in the first switch state, the second wheel109B is selectively used to provide additional motoring or brakingpower. In this switch state, battery 1102 is effectively disconnectedand, therefore, neither charges nor discharges.

[0128] When the second wheel 109B is not needed, switch controller 1120preferably places transfer switch 1104 in the second connectionstate—battery 1102 is connected to inverter 106B. If, at this time, theother traction motor (e.g., traction motor 108A) is operating in adynamic braking mode, electrical energy is generated and carried on DCtraction bus 122, as described in greater detail elsewhere herein.Inverter 106B transfers a portion of this dynamic braking electricalenergy to battery 1102 for storage. If, on the other hand, the othertraction motor is operating in a motoring mode, inverter 106B preferablytransfers any electrical energy stored in battery 1102 onto DC tractionbus 122 to supplement the primary electric power supplied by prime moverpower source 104. Such electrical energy transferred from battery 1102to DC traction bus 122 may be referred to as secondary electric power.In one embodiment, inverter 106B comprises a chopper circuit forcontrolling the provision of secondary electric power to DC traction bus122 from battery 1102.

[0129] It should be understood, however, that battery 1102 can also becharged when the other traction motors are not operating in a dynamicbraking mode. For example, the battery can be charged when transferswitch 1104 is in the second connection state (battery 1102 is connectedto inverter 106B) and the other traction motors are motoring or idlingif the amount of power drawn by the other traction motors is less thanthe amount of primary electric power carried on DC traction bus 122.

[0130] Advantageously, battery 1102 can also be charged using chargingelectric power from optional energy source 1130. As illustrated in FIG.11, optional energy source 1130 is preferably connected such that itprovides charging electric power to be carried on DC traction bus 122.When optional energy source 1130 is connected and providing chargingelectric power, switch controller 1120 preferably places transfer switch1104 in the second connection state. In this configuration, inverter106B transfers a portion of the electric power carried on DC tractionbus 122 to battery 1102 for storage. As such, battery 1102 may becharged from optional energy source 1130.

[0131] In summary, in the embodiment of FIG. 11, when transfer switch isin the second connection state, battery 1102 may be charged from dynamicbraking energy, from excess Off Highway Vehicle energy (i.e., when theother traction motors draw less power than the amount of primaryelectric power carried on DC traction bus 122), and/or from chargingelectric power from optional charging source 1130. When transfer switch1104 is in the second connection state and the other traction motordraws more power than the amount of primary electric power carried on DCtraction bus 122, inverter 106B transfers secondary electric power frombattery 1102 to DC traction bus 122 to supplement the primary electricpower. When transfer switch 1104 is in the first connection state,battery 1102 is disconnected and traction motor 1108B is operable toassist in motoring and/or dynamic braking. Table I summarizes one set ofoperating modes of the embodiment of FIG. 11. TABLE I One Axle Two AxlesLow Speed and Low Tractive Eff- Battery Fully Charged & Dynamic ortSettings Braking High Speed Motoring No Battery Charging & MotoringBattery Discharged & Motoring Very High Speed Dynamic Braking

[0132] While FIG. 11 illustrates an energy storage device in the form ofa battery, other energy storage devices, such as flywheel systems orultra-capacitors, may also be employed instead of or in addition tobattery 1102. Further, it should be understood that the configuration ofFIG. 11 may be scaled. In other words, the configuration can be appliedto more than one axle.

[0133] Although the foregoing descriptions have often referred to AC OffHighway Vehicle systems to describe several pertinent aspects of thedisclosure, the invention should not be interpreted as being limited tosuch Off Highway Vehicle systems. For example, aspects of the presentdisclosure may be employed with diesel-electric, fuel cell, “allelectric,” third-rail, trolley or overhead powered Off Highway Vehicles.Further, aspects of the hybrid energy Off Highway Vehicle systems andmethods described herein can be used with Off Highway Vehicles using aDC generator rather than an AC alternator and combinations thereof.Also, the hybrid energy Off Highway Vehicle systems and methodsdescribed herein are not limited to use with AC traction motors. Asexplained elsewhere herein, the energy management system disclosedherein may be used in connection with locomotives, mine trucks, largeexcavators, etc.

[0134] As can now be appreciated, the hybrid energy systems and methodsherein described provide substantial advantages over the prior art. Suchadvantages include improved fuel efficiency, increased fuel range, andreduced emissions such as transient smoke. Other advantages includeimproved speed by the provision of an on-demand source of power for ahorsepower burst. Significantly, the hybrid energy Off Highway Vehiclesystem herein described may also be adapted for use with existing OffHighway Vehicle systems.

[0135] When introducing elements of the invention or embodimentsthereof, the articles “a”, “an”, “the”, and “said” are intended to meanthat there are one or more of the elements. The terms “comprising”,“including”, and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

[0136] In view of the above, it will be seen that several aspects of theinvention are achieved and other advantageous results attained.

[0137] As various changes could be made in the above exemplaryconstructions and methods without departing from the scope of theinvention, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense. It is further to beunderstood that the steps described herein are not to be construed asnecessarily requiring their performance in the particular orderdiscussed or illustrated. It is also to be understood that additional oralternative steps may be employed.

1. A hybrid energy off highway vehicle power storage system, the systemcomprising: an off highway vehicle having a plurality of vehicle wheels;an off highway vehicle traction motor associated with one of theplurality of vehicle wheels, said off highway vehicle traction motorhaving a rotatable shaft mechanically coupled to the one of theplurality of vehicle wheels; an primary power source carried on the offhighway vehicle; an energy management processor; an electric powergenerator carried on the off highway vehicle, said generator responsiveto said processor and connected to and driven by the primary powersource for generating and selectively supplying primary electric powerto the off highway vehicle traction motor, said off highway vehicletraction motor being operable in response to the primary electric powerto rotate the rotatable shaft and to drive the one of the plurality ofvehicle wheels, said off highway vehicle traction motor further having adynamic braking mode of operation wherein the off highway vehicletraction motor generates electrical energy in the form of electricity;and an electrical energy capture system carried on the off highwayvehicle, said capture system responsive to said processor and inelectrical communication with the off highway vehicle traction motor forselectively storing electrical energy generated in the dynamic brakingmode and selectively providing secondary electric power from said storedelectrical energy to the traction motor to selectively supplement theprimary electric power with the secondary electric power so that saidoff highway vehicle traction motor is operable in response to theprimary off highway vehicle power and the secondary electric power;wherein the processor provides a first control signal to the capturesystem to control the selective storing of electrical energy generatedin the dynamic braking mode and to control the selective providing ofsecondary electric power to the off highway vehicle traction motor tosupplement the primary electric power, and provides a second controlsignal to the generator for controlling the selective supplying ofprimary electric power to the off highway vehicle traction motor.
 2. Thehybrid energy off highway vehicle power storage system of claim 1wherein the electrical energy capture system is in electricalcommunication with the electric power generator and selectively storesthe primary electric power, and wherein the energy management processorprovides the first control signal to the capture system to control theselective storing of primary electric power by the energy capturesystem.
 3. The hybrid energy off highway vehicle power storage system ofclaim 1 further comprising a charger external to the off highway vehiclesupplying charging electric power and wherein the electrical energycapture system is selectively connected to said charger such that theelectrical energy capture system stores the charging electric power whenconnected to the charger.
 4. The hybrid energy off highway vehicle powerstorage system of claim 1 further comprising; a charging power sourcecarried on the off highway vehicle having a power converter supplyingcharging electric power; and wherein the electrical energy capturesystem is selectively electrically connected to the power converter ofthe charging power source such that the electrical energy capture systemstores the charging electric power.
 5. The hybrid energy off highwayvehicle power storage system of claim 4 wherein the charging powersource is a fuel cell.
 6. The hybrid energy off highway vehicle powerstorage system of claim 1 wherein the electrical energy capture systemcomprises: an energy storage system for storing the electrical energygenerated in the dynamic braking mode; and an electrical powerconversion system for retrieving from the energy storage system thestored electrical energy and for providing the secondary electric power.7. The hybrid energy off highway vehicle power storage system of claim 6wherein the energy storage system comprises a battery system.
 8. Thehybrid energy off highway vehicle power storage system of claim 6wherein the energy storage system comprises a flywheel system.
 9. Thehybrid energy off highway vehicle power storage system of claim 6wherein the energy storage system comprises an ultracapacitor.
 10. Thehybrid energy off highway vehicle power storage system of claim 6wherein the energy storage system comprises an electrolysis cellgenerating and storing hydrogen.
 11. The hybrid energy off highwayvehicle power storage system of claim 1 further comprising: a resistivebraking grid; and a control circuit electrically connected to theresistive braking grid, the electrical energy capture system operatingsaid control circuit such that the control circuit selectively allowsthe electrical energy generated in the dynamic braking mode to bedissipated by the resistive braking grid.
 12. The hybrid energy offhighway vehicle power storage system of claim 11 wherein the controlcircuit comprises a chopper circuit and wherein the electrical energycapture system operates the chopper circuit at a duty cycle toselectively allow the electrical energy generated in the dynamic brakingmode to be dissipated by the resistive braking grid.
 13. The hybridenergy off highway vehicle power storage system of claim 1 wherein theelectric power generator comprises a DC traction bus, said DC tractionbus carrying the electrical energy generated in the dynamic braking modeand carrying the secondary electric power, said electrical energygenerated in the dynamic braking mode comprising DC electric power at afirst voltage level.
 14. The hybrid energy off highway vehicle powerstorage system of claim 13 wherein the electrical energy capture systemcomprises a first dc-to-dc converter electrically connected to the DCtraction bus, said first dc-to-dc converter converting the DC electricpower carried on the DC traction bus from the first voltage level to asecond voltage level.
 15. The hybrid energy off highway vehicle powerstorage system of claim 14 wherein the electrical energy capture systemfurther comprises a first electrical energy storage device connected tothe first dc-to-dc converter, said first electrical energy storagedevice receiving the DC electric power at the second voltage level fromthe first dc-to-dc converter.
 16. The hybrid energy off highway vehiclepower storage system of claim 15 wherein the electrical energy capturesystem further comprises: a second dc-to-dc converter electricallyconnected to the DC traction bus, said second dc-to-dc converterconverting the DC electric power carried on the DC traction bus from thefirst voltage level to a third voltage level; and a second electricalenergy storage device connected to the second dc-to-dc converter, saidsecond electrical energy storage device receiving the DC electric powerat the third voltage level from the second dc-to-dc converter.
 17. Thehybrid energy off highway vehicle power storage system of claim 16wherein the first and second energy storage devices comprise batteriesand wherein the first voltage level and the second voltage level aresubstantially the same.
 18. The hybrid energy off highway vehicle powerstorage system of claim 15 wherein the electrical energy capture systemfurther comprises a flywheel system electrically connected to the DCtraction bus and wherein the first electrical energy storage devicecomprises a battery system.
 19. The hybrid energy off highway vehiclepower storage system of claim 15 further comprising a battery bus andwherein the first dc-to-dc converter comprises a bi-directionalconverter converting the DC electric power carried on the DC tractionbus from the first voltage level to the second voltage level and whereinthe converted DC electric power at the second voltage level is carriedon the battery bus.
 20. The hybrid energy off highway vehicle powerstorage system of claim 19 wherein the first electrical energy storagedevice comprises a battery system electrically connected to the batterybus.
 21. The hybrid energy off highway vehicle power storage system ofclaim 20 wherein the electrical energy capture system further comprisesa flywheel system.
 22. The hybrid energy off highway vehicle powerstorage system of claim 21 wherein the flywheel system is connected inparallel with the battery system.
 23. The hybrid energy off highwayvehicle power storage system of claim 14 further comprising: anauxiliary power bus supplying auxiliary electrical power to an auxiliaryelectrical system associated with the off highway vehicle; wherein thefirst dc-to-dc converter comprises a bi-directional converter convertingthe DC electric power carried on the DC traction bus from the firstvoltage level to the second voltage level and wherein the converted DCelectric power at the second voltage level is carried on the auxiliarypower bus; and wherein the electrical energy capture system furthercomprises a first electrical energy storage device, said firstelectrical energy storage device and said first dc-to-dc converter beingconnected in parallel across the DC traction bus.
 24. The hybrid energyoff highway vehicle power storage system of claim 23 wherein the firstelectrical energy storage device comprises a battery system and thesecond electrical energy storage device comprises a flywheel system. 25.The hybrid energy off highway vehicle system of claim 23 furthercomprising a second electrical energy storage device, said first andsecond electrical energy storage devices being connected in parallelacross the DC traction bus.
 26. The hybrid energy off highway vehiclepower storage system of claim 1 wherein the electrical energy capturesystem comprises: a power converter electrically connected to the DCtraction bus; a first storage device selectively storing a first portionof the electrical energy generated in the dynamic braking mode; a secondstorage device selectively storing a second portion of the electricalenergy generated in the dynamic braking mode; and wherein the powerconverter transfers part of the first portion of the electrical energygenerated in the dynamic braking mode stored in the first storage deviceto the second storage device.
 27. The hybrid energy off highway vehiclepower storage system of claim 26 wherein the first storage devicecomprises a flywheel system and the second storage device comprises abattery system.
 28. The hybrid energy off highway vehicle power storagesystem of claim 26 wherein the first and second storage devices comprisebattery systems.
 29. The hybrid energy off highway vehicle power storagesystem of claim 1 wherein the primary power source is a diesel engine.30. The hybrid energy off highway vehicle power storage system of claim1 wherein the primary power source is a fuel cell.
 31. The hybrid energyoff highway vehicle power storage system of claim 1, wherein the offhighway vehicle is a locomotive.
 32. The hybrid energy off highwayvehicle power storage system of claim 1, wherein the off highway vehicleis a mine truck.
 33. A hybrid energy off highway vehicle system for usein connection with a off highway vehicle for propelling the off highwayvehicle, said system comprising: a primary power source carried on theoff highway vehicle; an energy management processor; a power converterdriven by the primary power source for selectively providing primaryelectric power and responsive to said processor; a traction bus coupledto the power converter and carrying the primary electric power; an offhighway vehicle traction system coupled to the traction bus, said offhighway vehicle traction system having a motoring mode and a dynamicbraking mode, said off highway vehicle traction system propelling theoff highway vehicle in response to the primary electric power in themotoring mode and said off highway vehicle traction system generatingelectrical energy in the dynamic braking mode; and an electrical energystorage system carried on the off highway vehicle, responsive to saidprocessor, said electrical energy storage system coupled to the tractionbus selectively capturing electrical energy generated by the off highwayvehicle traction system in the dynamic braking mode and selectivelytransferring the captured electrical energy as secondary electric powerto the off highway vehicle traction system to augment the primaryelectric power in the motoring mode, and said off highway vehicletraction system propelling the off highway vehicle in response to thesecondary electric power; and wherein the processor provides a firstcontrol signal to the electrical energy storage system to control theselective storing of electrical energy generated in the dynamic brakingmode and to control the selective providing of secondary electric powerto the off highway vehicle traction motor to supplement the primaryelectric power, and provides a second control signal to the powerconverter for controlling the selective supplying of primary electricpower to the off highway vehicle traction motor.
 34. The hybrid energyoff highway vehicle system of claim 33 wherein the off highway vehicletraction system comprises an off highway vehicle inverter and an offhighway vehicle traction motor, said off highway vehicle inverter beingelectrically coupled to the traction bus and responsive to the primaryelectric power to provide drive power, said off highway vehicle tractionmotor being electrically coupled to the off highway vehicle inverter andpropelling the off highway vehicle in response to the drive power. 35.An electrical energy capture system for use in connection with a hybridenergy off highway vehicle system of a off highway vehicle, the hybridenergy off highway vehicle system includes an off highway vehicle, aprimary power source, and an off highway vehicle traction motorpropelling the off highway vehicle in response to the primary electricpower, said off highway vehicle traction motor having a dynamic brakingmode of operation generating electrical energy, the electrical energycapture system comprising: an energy management processor carried on theoff highway vehicle; an off highway vehicle electric generator connectedto and driven by the primary power source for selectively supplyingprimary electric power, wherein the generator is responsive to saidprocessor; and an electrical energy storage device carried on a offhighway vehicle in electrical communication with the off highway vehicletraction motor and responsive to said processor, said electrical energystorage device selectively storing electrical energy generated in thedynamic braking mode, and said electrical energy storage deviceselectively providing secondary electric power from said storedelectricity electrical energy to the off highway vehicle traction motor,said off highway vehicle traction motor being responsive to thesecondary electric power; wherein the processor provides a first controlsignal to the electrical energy storage device to control the selectivestoring of the electrical energy generated in the dynamic braking mode,and to control the selective providing of secondary electric power tothe off highway vehicle traction motor, and provides a second controlsignal to the generator for controlling the selective supplying ofprimary electric power to the off highway vehicle traction motor. 36.The energy capture system of claim 35 further comprising; a chargingpower source carried on the off highway vehicle; a charging power sourcepower converter driven by the charging power source, said charging powersource power converter providing charging electric power; and thecharging power source power converter responsive to the energymanagement processor for selectively providing charging electric powerto said electrical energy storage device for storing charging electricpower.
 37. The energy capture system of claim 35 wherein the electricalenergy storage device selectively receives the primary electric powerand selectively stores the received primary electric power therein, andwherein the energy management processor provides the first controlsignal to the energy storage device to control the selective storing ofprimary electric power.
 38. The energy capture system of claim 35further comprising: a charger external to the off highway vehiclesystem, said charger being configured to be selectively electricallycoupled to the energy storage device and to provide charging electricpower thereto and wherein the energy storage device selectively storesthe charging electric power when coupled to the charger.